This K08 application is submitted by Qi Cao, M.D., Ph.D., Assistant Professor of Diagnostic Radiology and Nuclear Medicine at the University of Maryland School of Medicine. My long term goal is to become an independent investigator focusing on establishing a reliable and reproducible PET/CT technique to noninvasively and specifically diagnose early-stage alcoholic liver fibrosis (ALF). Toward this goal, I propose a mentored career development plan which provides the following training in: 1) preclinical experiments to assess specific cellular tracer uptake in vitro, 2) in new radiotracer synthesis and preclinical imaging in order to quantify biodistribution and dosimetry, and 3) in functional molecular imaging for the diagnosis of early stage liver fibrosis. SPECIFIC AIMS: The first aim is to evaluate the role of proline in collagen synthesis using 3H-labeled proline in an in vitro culture system of hepatic stellate cells (HSCs) isolated from livers of animals with alcoholic steatosis (AS), alcoholic steatohepatitis (ASH), early stage alcoholic liver fibrosis (EAF), and late stage alcoholic liver fibrosis (LAF) by using beta counting. The second aim is to establish dynamic 18F-proline PET imaging to assess radiotracer biodistribution in 12 critical organs/tissues and to optimize dosing and timing conditions which will translate this procedure to image ALF in animals with AS, ASH, EAF, and LAF as described in Aim 3. The third aim is to study the role of 18F-proline in the diagnosis of early-stage liver fibrosis in HSC from animals with AS, ASH, EAF, and LAF by static 18F-proline PET/CT imaging. The proposed complementary approaches in the specific aims will help to: (1) establish important parameters of 18F-proline labeling by optimizing tracer dosing and imaging timing conditions; and (2) determine the experimental importance of 18F-proline in the assessment of collagen production in in vitro (aim 1) and in vivo (aims 2 and 3) models, which will provide a new means to assess early liver fibrosis in patients with ALD. This line of investigation will use functional imaging to fill critical gaps in the mechanism of in vivo collagen production, which will further our understanding of liver disease and advance clinic treatment by providing a noninvasive means to diagnose early-stage liver fibrosis at a stage before damage becomes permanent. Through intensive training in the application of non-invasive molecular imaging to ALD, I will gain the expertise required of an independent investigator to apply molecular imaging to the study and diagnosis of liver disease. RELEVANCE: The project will use noninvasive 18F-proline PET/CT imaging to correlate radiotracer incorporation activity within scar formation cells with scar collagen formation. The ability to image scar formation will provide valuable data to enable the development of this technique for noninvasive identification of early-stage liver disease during routine patient care, which will greatly advance the treatment of liver disease.